STATE OF CHARGE DEPENDENT EXCHANGE CURRENT DENSITY AND VOLTAGE HYSTERESIS IN SILICON ANODE LITHIUM CELLS

Abstract

In this study, three types of silicon anode-based coin cells—porous, nano, and bulk—were fabricated and subjected to lithiation-delithiation cycling tests. A notable capacity difference was observed between the start and end points of the battery cycling loop. This discrepancy was mitigated using a side-reaction correction technique applied to the exchange current density via the Tafel kinetics formula. Significant voltage hysteresis was detected during the cycling of all three cell types. A physics-based mathematical model was developed to identify the primary cause of this voltage hysteresis. The influence of hydrostatic stress on the hysteresis was examined, revealing that stress-induced voltage values were too low to significantly impact hysteresis. Subsequently, key parameters controlling this stress were identified. New exchange current density equations (average, linear, and logarithmic) were formulated as functions of the State of Charge (SOC). The application of the logarithmic SOC-dependent exchange current density equation showed the best fit with experimental results, demonstrating that controlling this SOC-based equation can minimize voltage hysteresis. This study provides detailed insights into the mechanisms behind voltage hysteresis in silicon anode-based lithium half cells